This present invention relates to internal exhaust gas re-circulation and more particularly to a system for providing internal exhaust gas re-circulation with a compression release brake actuator.
Exhaust gas re-circulation systems have been utilized to control emissions and reduce undesirable gasses and particulate matter to the atmosphere. Such engines have been used in an assortment of applications, such as, on highway, off highway and other internal combustion engine powered mobile equipment.
Exhaust gas re-circulation systems (EGR) typically direct a portion of the exhaust gases emitted from an internal combustion engine to a combustion chamber of the engine by way of an EGR valve disposed in and elaborate external system of ducting and other components. The exhaust gas which is directed to the combustion chamber reduces the concentration of oxygen in the combustion chamber. This reduction in the concentration of oxygen lowers the maximum combustion temperature within the cylinder, slows the chemical reaction of the combustion process and decreases the formation of nitrous oxides (NOx).
Exhaust gasses also contain unburned hydrocarbons. By reintroducing a portion of the exhaust gasses to the combustion chamber the unburned hydrocarbons are subsequently burned. This further reduces the emission of exhaust gas by-products which would otherwise be emitted as undesirable pollutants from the internal combustion engine.
Internal combustion engines often include a turbocharger(s) to increase engine performance. Such devices utilize exhaust gases to drive a turbine disposed in the exhaust gas stream of the engine. The turbine is connected to and powers a compressor which boosts the pressure of air supplied to the inlet manifold of the engine. In turbocharged engines, the EGR valve directs a portion of the exhaust gases by way of the ducting from an exhaust manifold of the engine to an inlet of the compressor. This may result in the fouling of the turbocharger compressor and an intercooler of the engine, when such is provided.
U.S. Pat. No. 6,012,424 to Zdenek Meistrick, dated Jan. 11, 2000 discloses an apparatus to accomplish exhaust gas re-circulation and/or engine braking. This patent discloses an elaborate and complicated system of actuators, control valves and fluid pressure sources defining separate EGR and compression release operating circuits which communicate with and control a slave piston to actuate at least one exhaust valve. Since the operating circuits are dependent on one another to trigger compression release braking and EGR system flexibility is limited. For example, a full range of EGR may not be supplied to the engine.
This invention is directed at overcoming one or more of the problems set forth above.
In one embodiment, a compression release brake actuating system for achieving compression release braking and internal exhaust gas re-circulation in an internal combustion engine having a cylinder, a bore in the cylinder and a piston slidably disposed in the bore and movable relative to the cylinder between a top dead center position and a bottom dead center position. A cylinder head is connected to the cylinder and an exhaust manifold is connected to the cylinder head. A combustion chamber is defined by the cylinder head, piston and cylinder. An exhaust valve is connected to the cylinder head and movable between a closed position and an open position. The exhaust valve has substantially zero lift relative to the cylinder head at the closed position and a predetermined maximum amount of lift relative to the cylinder head at the open position. The exhaust valve is adapted to pass exhaust gas between the combustion chamber and the exhaust manifold at the open position and is adapted to block the passing of exhaust gas between the exhaust manifold and the combustion chamber at the closed position. An intake valve is connected to the cylinder head and is movable between a closed position and an open position, said intake valve having substantially zero lift relative to the cylinder head at the closed position and a predetermined maximum amount of lift relative to the cylinder head at the open position. The intake valve is adapted to pass intake fluid flow between said intake manifold and the combustion chamber at the open position of the intake valve and adapted to block the passing of intake fluid flow between the combustion chamber and the intake manifold at the closed position of the intake valve. A camshaft is operatively connected to move the intake and exhaust valves between the closed and open positions. The camshaft determines the maximum amount of lift of each of the exhaust and intake valves at the open position. The exhaust valve is movable to the open position during movement of the piston within a first predetermined range of piston movement and the intake valve is movable to the open position during movement of the piston within a second predetermined range of piston movement. A compression release brake actuator is operatively connected to the exhaust valve and actuatable to maintain the exhaust valve at an intermediate lift position having a magnitude between the maximum amount of lift and the closed position during a predetermined portion of at least one of the first and second ranges of piston movement and providing a re-circulation of the exhaust gas between the exhaust manifold and the combustion chamber.
In another embodiment, an internal combustion engine includes a cylinder having a bore and a piston slidably disposed in the cylinder bore and movable relative to the cylinder between a top dead center position and a bottom dead center position. A cylinder head is connected to the cylinder. An exhaust manifold is connected to the cylinder head. A combustion chamber is defined by the cylinder head, the piston and the cylinder. An exhaust valve is connected to the cylinder head and movable between a closed position and an open position. The exhaust valve has substantially zero lift relative to the cylinder head at the closed position and a predetermined maximum amount of lift relative to the cylinder head at the open position. The exhaust valve is adapted to pass exhaust gas between the combustion chamber and the exhaust manifold at the open position and adapted to block the passing of exhaust gas between the exhaust manifold at the closed position. An intake valve is connected to the cylinder head and movable between a closed position and an open position. The intake valve has substantially zero lift relative to the cylinder head at the closed position and has a predetermined maximum amount of lift relative to said cylinder head at the open position. The intake valve is adapted to pass intake fluid flow between the intake manifold and the combustion chamber at the open position of the intake valve and being adapted to block the passing of intake fluid flow between the combustion chamber and the intake manifold at the closed position of the intake valve. A camshaft is operatively connected to move the intake and exhaust valves between the closed and open positions. The camshaft determines the maximum amount of lift of each of the exhaust and intake valves at the open position. The exhaust valve is movable to the open position during movement of the piston within a first predetermined range of piston movement and the intake valve is movable to the open position during movement of the piston within a second predetermined range of piston movement. A compression release brake actuator is operatively connected to said exhaust valve and being actuatable during said first predetermined range of piston movement to modify the movement of the exhaust valve between said open and closed positions and maintain the exhaust valve at said intermediate position during at least a portion of the first range of piston movement and during a portion of a second range of piston movement and provide a re-circulation of the exhaust gas between the exhaust manifold and the combustion chamber.
In yet another embodiment, a method of controlling internal exhaust gas re-circulation in an internal combustion engine having a compression release brake actuator, an exhaust valve, an intake valve, an exhaust manifold, a cam shaft operatively connected to move said exhaust valve between an open position at which the exhaust valve is at a maximum lift position and a closed position, a combustion chamber defined by a piston, a cylinder and a cylinder head, The piston being movable between a top dead center position and a bottom dead center position, including the steps of: moving the exhaust valve mechanically with the camshaft from the closed position to the open position in response to the piston being at a first predetermined range of piston movement; moving the intake valve mechanically by the camshaft from the closed position to the open position in response to the piston being at a second predetermined range of piston movement different than said first predetermined range of piston movement; actuating the compression release brake actuator in response to the piston being at a predetermined position within at least one of the predetermined first and second predetermined ranges of piston movement; maintaining the exhaust valve at the intermediate lift position subsequent to actuation of the compression release brake actuator and during a predetermined range of piston movement; and passing exhaust gas between the exhaust manifold and the combustion chamber while the exhaust valve is at the intermediate position.